Blood Type is Controlled by 3 Alleles

Alleles: A, B, O
A & B are codominant
O is recessive

What genotypes are possible for each of the blood types?

Type A
Type B
Type AB
Type O

Sample Family:
Mom is type O, Dad is type A
Daughter is type A, son is type O.
Show a Punnett square for this family:

Why is type "O" the universal donor?

*The antigens on the surface of your cells (or donated cells) will cause a reaction if your immune system does not recognize them as being part of you. Hence, if you are Type A, and transfused with Type B, your body will mobilize a massive immune response against the "invading" blood. This will cause coagulation (agglutination) of blood and death.

Each blood group has different antigens on its surface. These antigens could trigger an immune response (antibodies) in transfusion recipients.

blood type chart

Look at the chart: Explain why Type "O" blood can be donated to anyone.
Why is AB called the "universal acceptor"?

What blood types could a person with Type O blood accept?

Rh Factor (Rh = rhesus monkey)

A person can have surface Rh antigens (and be Rh +) or no antigens (and be Rh - )

Erythroblastosis fetalis - antibodies in the mother's blood attack the fetus, usually in 2nd pregnancies.

Image Source:

Blood Safety

Blood can carry diseases and health care professionals must be careful when working with blood.
A bloodborne pathogen is any disease causing agent that is present in the blood and can be transferred from one person to another.

Examples of blood borne pathogens:

Testing Your Blood

A test kit can be used to test your blood type. It involves pricking your finger and placing a drop of blood on a card that will react to a serum on the card that contains antibodies. You will be given the opportunity to test your blood type using this technique.